.app{
    height: 100%;
}
.loading{
    position: absolute;
    width: 100%;
    left: 50%;
    top: 50%;
    -webkit-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
    
}
.loading img{
    width: 100%;
    text-align: center;
}
.header{
    position: sticky;
    top: 0;
    z-index: 99;
}